The blond beauty is celebrating her 45th birthday today and in honor of the Bridget Jones star, we're taking a look back at her style transformation over her years in Tinseltown.

From her early days starring in Jerry McGuire to her more recent work in Cinderella Man, the thesp is no stranger to switching up her style while still looking stunning on each and every red carpet.

In March, the actress made her first red carpet appearance in four months, looking gorgeous in a fitted black dress and matching peep toe pumps which she accessorized with classic pearls while wearing her hair up in a messy bun.

But that's hardly the first time Zellweger has turned heads! Here's a look back at her style transformation:

1. Flashback Photo: The actress wears a gorgeous purple gown to the Jerry McGuire premiere, held in NYC. She completes the look with minimal makeup and sports her signature bob hairstyle.

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2. Beautiful Bridget Jones: A raven-haired Renée looks ravishing in a bright red dress at the premiere of Bridget Jones: The Edge of Reason in France back in 2004. The corset style accentuates her tiny waist while the strapless look highlights her toned and trim frame.

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3. All That Jazz: Zellweger, who played Roxie Hart, in the hit flick Chicago, sasses up the red carpet in a fun and flirty black frock at the film's London premiere. Her bob hairstyle perfectly completes the look in addition to her megawatt smile.

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4. Golden Goddess: The actress is the belle of the ball at the 2013 Academy Awards, where she stunned in a gold custom Caroline Herrera gown. Her hair is swept up into a messy updo and she adds a stack of dazzling bracelets to finish off the beautiful style.

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5. Punk It Up: The actress attends the punk-themed Met Gala held at the Metropolitan Museam of Art in NYC wearing a Prada dress and Louboutin shoes. While the blonde stunner may not have quite followed the theme, we think the fitted frock still looks fabulous.